Electronic Appliance and Light-Emitting Device

ABSTRACT

An EL element having a novel structure is provided, which is suitable for AC drive. A light-emitting element of the invention is provided with material layers (material layers each having approximately symmetric I-V characteristics with respect to the zero point in a graph having the abscissa axis showing current values and the ordinate axis showing voltage values) between a first electrode and a layer including an organic compound and between the layer including the organic compound and a second electrode respectively. Specifically, each of the material layers is a composite layer including a metal oxide and an organic compound.

This application is a divisional of copending application Ser. No.11/291,312 filed on Dec. 1, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light-emitting elementhaving an anode, a cathode and a layer including an organic compound,which emits light when an electronic field is applied thereto(hereinafter referred to as an ‘electroluminescent layer’), and alight-emitting device using such an organic light-emitting element. Inaddition, the invention relates to an electronic appliance mounted withthe light-emitting device having an organic light-emitting element asits component.

2. Description of the Related Art

In recent years, a light-emitting device having an EL element as aself-luminous element has been actively developed. This light-emittingdevice is also called an organic EL display or an organic light-emittingdiode. Such a light-emitting device has advantages in that low-voltageand low-power-consumption drive can be performed with high responsespeed which is suitable for displaying moving images. Therefore, thelight-emitting device has been attracting attention as a next-generationdisplay such as a new-generation portable phone or portable informationterminal (PDA).

The light-emitting element has a pair of electrodes (an anode and acathode) and an electroluminescent layer interposed therebetween. It issaid that light emission is obtained when a hole injected from the anodeand an electron injected from the cathode upon application of anelectronic field to the both electrodes are recombined in theluminescent center of the electroluminescent layer, thereby a molecularexciton is formed to release energy in returning to the ground state.

The organic EL display having a light-emitting element is aself-luminous type differently from a liquid crystal display whichrequires a backlight, thus it has no problem with regard to the viewingangle. That is, the organic EL display is more suitable for a displayfor outdoor use than a liquid crystal display, and various applicationsthereof have been proposed.

A driving method of the organic EL display can be roughly classifiedinto Direct Current (DC) drive and Alternate Current (AC) drive.

The present applicant has disclosed Patent Document 1 in which AC driveis used in an active matrix display device having an EL element, anddisclosed Patent Document 2 in which an EL element is used for the ACdrive.

[Patent Document 1] Japanese Patent Laid-Open No. 2001-222255

[Patent Document 2] Japanese Patent Laid-Open No. 2004-95546

When AC drive is performed, an AC signal (signal of which voltage levelis inverted in regular cycles) is applied to a pair of electrodes of anEL element. In the case where the EL element has a simple structure suchas a stacked-layer structure of a first electrode, a second electrodeand a layer including an organic compound interposed therebetween, lightemission is obtained only in a half cycle when an AC signal is appliedthereto due to the rectifying function. Accordingly, in order to obtainabout an equal amount of light to the case of performing DC drive inwhich DC voltage is applied to the EL element, power consumption isincreased.

SUMMARY OF THE INVENTION

It is a primary object of the invention to provide an EL element havinga novel structure which is suitable for AC drive.

A light-emitting element according to the invention has a novelstructure suitable for the AC drive, where material layers (materiallayers each having approximately symmetric current-voltage (I-V)characteristics with respect to the zero point in a graph having theabscissa axis showing current values and the ordinate axis showingvoltage values) are provided between a first electrode and a layerincluding an organic compound and between the layer including theorganic compound and a second electrode respectively.

The material layers having the aforementioned I-V characteristics haveboth a hole injection (a hole transporting) property and an electroninjection (or electron transporting) property, and one of the propertiesbecomes dominant in accordance with an AC signal applied.

An applied AC signal has, as shown in an example of a waveform in FIG.13, the same absolute value of voltage on the positive side and thenegative side. Therefore, the luminance of an EL element in a half cyclein which a positive voltage is applied is required to be equal to theluminance of the EL element in another half cycle in which a negativevoltage is applied. Thus, according to the invention, by using materiallayers each having approximately symmetric I-V characteristics withrespect to the zero point in a graph having the abscissa axis showingcurrent values and the ordinate axis showing voltage values, an ELelement can be controlled to emit light in accordance with both positiveand negative signals being applied. Further, about an equal amount oflight to the case of performing DC drive in which DC voltage is appliedto the EL element can be obtained without increasing power consumption.

A light-emitting device in accordance with the structure of theinvention includes a plurality of light-emitting elements. Each of thelight-emitting elements includes a first electrode; a first materiallayer formed over the first electrode; a layer including an organiccompound formed over the first material layer; a second material layerformed over the layer including the organic compound; and a secondelectrode formed over the second material layer. The first materiallayer has approximately symmetric I-V characteristics with respect tothe zero point in a graph having the abscissa axis showing currentvalues and the ordinate axis showing voltage values, and the secondmaterial layer has the same I-V characteristics as the first materiallayer.

In the aforementioned structure, each of the first material layer andthe second material layer is a composite layer of an organic compoundand an inorganic compound which can give/receive electrons to/from theorganic compound. Specifically, it is a composite layer including ametal oxide and an organic compound.

In the aforementioned structure, the metal oxide is one or more ofmolybdenum oxide, tungsten oxide and rhenium oxide.

The aforementioned first and second material layers can have excellentconductivity in addition to an effect (improvement in heat resistanceand the like) which is considered to be obtained by mixing an inorganiccompound therewith. Such effects cannot be obtained only by mixing anorganic compound and an inorganic compound having no electronic mutualinteraction with each other like a conventional hole transporting layer.

The aforementioned first and second material layers can be formed thickwithout causing an increase in the driving voltage; therefore, a shortcircuit of elements which derives from dust or the like in the formationprocess of the EL element can be suppressed, thereby the yield can beimproved.

Needless to say, the aforementioned first and second material layers maybe formed using materials having different compositions as long as thematerials have the aforementioned I-V characteristics. Theaforementioned first and second material layers are not specificallyrequired to have the same thickness.

Since the material layers having the aforementioned I-V characteristicshave both the hole injection (or hole transporting) property and theelectron injection (or electron transporting) property, the structure ofthe EL element can be simplified. For example, such a complex structureis not required that a layer which emits light per half cycle inaccordance with an AC signal be provided between a pair of electrodes,thereby a manufacturing process can be simplified.

In the light-emitting device having the aforementioned structure, adriver circuit for applying an AC signal between the first electrode andthe second electrode is provided. If a video signal of whichpositive/negative levels are inverted in regular cycles is appliedbetween the first electrode and the second electrode of thelight-emitting device, image display can be performed as an organic ELdisplay. Note that the regular cycle defined herein is based on thecycle of a vertical synchronizing signal or a horizontal synchronizingsignal. For example, the regular cycle is set to be equal to or longerthan 1/60 seconds. If the regular cycle is set to be shorter then 1/60seconds, the light-emitting device can be more suitable for displayingmoving images.

Note that a light-emitting device in this specification means an imagedisplay device, a light-emitting device and a light source (including alighting device). In addition, the light-emitting device includes all ofa module in which a light-emitting device is connected to a connectorsuch as an FPC (Flexible Printed Circuit), a TAB (Tape AutomatedBonding) tape or a TCP (Tape Carrier Package), a module in which aprinted wiring board is provided on the tip of a TAB tape or a TCP, anda module in which an IC (Integrated Circuit) is directly mounted onto alight-emitting element by COG bonding

According to the invention, a light-emitting device suitable for ACdrive can be realized without complicating an element structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a structure of a light-emitting elementof the invention.

FIG. 2 illustrates an operating mechanism of a light-emitting element ofthe invention.

FIG. 3 illustrates an operating mechanism of a light-emitting element ofthe invention.

FIG. 4 is a graph showing the I-V characteristics of a material layer ofthe invention.

FIG. 5A illustrates a top structure of a passive display device andFIGS. 5B and 5C illustrate cross-sectional structures thereof.

FIG. 6 is a perspective view after the formation of inversely taperedpartition walls.

FIG. 7 is a top external view of a light-emission module.

FIGS. 8A and 8B are top views of a light-emitting module.

FIG. 9 is a cross-sectional view of a light-emitting module.

FIGS. 10A to 10C are cross-sectional views of a light-emitting module.

FIG. 11 illustrates an example of an electronic appliance.

FIGS. 12A to 12G illustrate examples of an electronic appliance.

FIG. 13 is a graph showing an AC signal.

FIG. 14A is a graph showing the I-V characteristics in the case of usinga single organic compound layer while FIG. 14B is a graph showing theI-V characteristics in the case of using a single molybdenum oxide layer(comparative example).

DETAILED DESCRIPTION OF THE INVENTION

Although the invention will be fully described by way of embodiment modeand embodiments with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the invention, they should beconstrued as being included therein. FIG. 1 shows an example of astacked-layer structure of a light-emitting element of the invention.

FIG. 1 shows a structure in which a first electrode 11, a first materiallayer 12, a layer including an organic compound 13, a second materiallayer 14 and a second electrode 15 are stacked in this order over asubstrate 10 having an insulating surface. Note that an AC power source16 is connected to the first electrode 11 and the second electrode 15 sothat the layer including an organic compound 13 emits light.

One or both of the first electrode 11 and the second electrode 15 areformed using a light-transmissive conductive film. As alight-transmissive conductive film, ITO, TZO, ITSO or the like may beused. Each of the first electrode 11 and the second electrode 15 isformed with a thickness of 10 to 500 nm. If the first electrode 11 andthe second electrode 15 are each thinner than 10 nm, they do notfunction as the electrodes since the conductivity is drasticallylowered. Meanwhile, if the first electrode 11 and the second electrode15 are each thicker than 500 nm, light transmissivity is lowered.

In the case of using a metal film as the first electrode 11 or thesecond electrode 15, Ag, Al, Ta or the like, may be used.

Each of the first material layer 12 and the second material layer 14 isformed using a material having approximately symmetric I-Vcharacteristics with respect to the zero point in a graph having theabscissa axis showing current values and the ordinate axis showingvoltage values. Specifically, each of the first material layer 12 andthe second material layer 14 is formed as a composite layer of a metaloxide (e.g., molybdenum oxide, tungsten oxide or rhenium oxide) and anorganic compound material having a hole transporting property (e.g.,N,N′-bis(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine(abbreviated as TPD), 4,4′-bis[N-(1-napthyl)-N-phenyl-amino]biphenyl(abbreviated as α-NPD) or4,4′-bis[N-[4-{N,N-bis(3-methylphenyl)amino}phenyl]-N-phenylamino]biphenyl(abbreviated as DNTPD)).

The thickness of the first material layer 12 and the second materiallayer 14 is each set in the range of 3 to 1000 nm. If these layers arethinner than 3 nm, they cannot be formed over the entire surface.Meanwhile, if these layers are thicker than 1000 nm, the lighttransmissivity is drastically lowered.

The layer including the organic compound 13 may have either a singlelayer or stacked layers, and the thickness of each layer included in thelayer including the organic compound 13 is set in the range of 5 to 500nm. In the structure of the light-emitting element in FIG. 1, an evensimpler stacked-layer structure is obtained in the case of adopting asingle layer.

The layer including the organic compound 13 may be formed using, forexample, tris(8-quinolinolato) aluminum (abbreviated as Alq₃),tris(4-methyl-8-quinolinolato) aluminum (abbreviated as Almq₃) or α-NPD.Alternatively, the layer including the organic compound 13 may be formedto contain a dopant material such as N,N′-dimethyl quinacridone(abbreviated as DMQd), Coumarin 6 or rubrene.

The layer including the organic compound 13 is preferably formed using amaterial having a highest occupied molecular orbital (HOMO) and a lowestunoccupied molecular orbital (LUMO) of which levels are within the rangeof a bandgap of the metal oxides contained in the first material layer12 and the second material layer 14.

In addition, each material of the first electrode 11 and the secondelectrode 15 preferably has a work function within the range of abandgap of the metal oxides contained in the first material layer 12 andthe second material layer 14.

Description is made below on the operating mechanism of light emissionin which an AC signal is applied to the light-emitting element shown inFIG. 1 from the AC power source 16 and light emission is obtained byutilizing energy levels shown in FIGS. 2 and 3. Note that portions inFIGS. 2 and 3 which correspond to those in FIG. 1 are denoted by thesame reference numerals.

FIG. 2 shows an example of the state of energy levels where the firstelectrode 11 of the light-emitting element is formed of ITO while thesecond electrode 15 thereof is formed of Al.

When a voltage is applied between the first electrode 11 and the secondelectrode 15, charges are generated in the first material layer 12 andthe second material layer 14. Among the charges generated in the firstmaterial layer 12 in contact with the first electrode 11, electrons moveto the first electrode 11 whereas holes are injected into the layerincluding the organic compound 13.

On the other hand, among the charges generated in the second materiallayer 14 in contact with the second electrode 15, electrons are injectedinto the layer including the organic compound 13 whereas holes move tothe second electrode 15.

In this manner, the holes injected from the first material layer 12 andthe electrons injected from the second material layer 14 are recombinedto emit light in the layer including the organic compound 13.

FIG. 3 shows the state of energy levels in which a signal having anopposite voltage level (positive or negative voltage) to the one shownin FIG. 2 is applied. Even when a signal having the opposite voltagelevel is applied, light emission is similarly obtained in the layerincluding the organic compound 13 since the element structure is thesame.

As set forth above, when an AC signal is applied to the light-emittingelement of the invention, light emission can be obtained not only in ahalf cycle in which either a positive or negative voltage is applied butalso in another half cycle in which a voltage having the opposite levelis applied.

FIG. 4 shows a result obtained from the following experiment.

A sample 1 (a stack of an ITSO film, a composite film obtained bysimultaneously vapor-depositing molybdenum oxide, DNTPD and rubrene atan arbitrary ratio, and an aluminum film, which is fowled over a glasssubstrate) and a sample 2 (a stack of an ITSO film, a composite filmobtained by simultaneously vapor-depositing molybdenum oxide, BBPB andrubrene at an arbitrary ratio, and an aluminum film, which is formedover a glass substrate) are manufactured.

Current and voltage are applied to the sample 1 and the sample 2, eachof which is plotted in a graph having the abscissa axis showing currentvalues and the ordinate axis showing voltage values.

It can be seen from the graph shown in FIG. 4 that the material layerinterposed between a pair of electrodes (the ITSO film and the aluminumfilm) of the sample 1 has approximately symmetric I-V characteristicswith respect to the zero point. Similarly, the material layer of thesample 2 has approximately symmetric I-V characteristics with respect tothe zero point.

As a comparative example 1, FIG. 14A shows a result obtained bymeasuring the I-V characteristics after stacking an ITSO film, a DNTPDfilm and an aluminum film over a glass substrate. In addition, as acomparative example 2, FIG. 14A also shows a result obtained bymeasuring the I-V characteristics after stacking an ITSO film, a BBPBfilm and an aluminum film over a glass substrate. As shown in FIG. 14A,when an organic compound film having a single layer is interposedbetween a pair of electrodes, current flows only when a positive voltageis applied thereto.

As a comparative example 3, FIG. 14B shows a result obtained bymeasuring the I-V characteristics after stacking an ITSO film, amolybdenum oxide film and an aluminum film over a glass substrate. Asshown in FIG. 14B, when a molybdenum oxide film having a single layer isinterposed between a pair of electrodes, symmetric I-V characteristicswith respect to the zero point are not obtained.

In the following embodiments, mode detailed description is made on thestructure of the invention.

Embodiment 1

FIGS. 5A to 5C show an example where the structure of a light-emittingelement of the invention is used as a light-emitting element of apassive matrix display device.

FIG. 5A is a top view of a pixel portion before being sealed, FIG. 5B isa cross-sectional view along a dashed line A-A′ of FIG. 5A, and FIG. 5Cis a cross-sectional view along a dashed line B-B′ of FIG. 5A.

Over a first substrate 110, a plurality of first electrodes 113 aredisposed in stripes at regular intervals. Over each of the firstelectrodes 113, a partition wall 114 having an opening corresponding toeach pixel is provided. The partition wall 114 having an opening isformed of a photosensitive or non-photosensitive organic material (e.g.,polyimide, acrylic, polyamide, polyimide amide, resist orbenzocyclobutene), or an SOG film (e.g., a SiO_(x) film containing analkyl group). Note that the opening corresponding to each pixel is alight-emitting region 121.

Over the partition walls 114 each having an opening, a plurality ofinversely tapered partition walls 122 are provided in parallel, whichextend in a direction to intersect the first electrodes 113. Theinversely tapered partition walls 122 are formed by photolithographyusing a positive photosensitive resin (by which an unexposed portionremains as a pattern) and controlling the amount of light exposure ordeveloping time in such a manner that a portion below the pattern isetched more.

FIG. 6 shows a perspective view immediately after forming the pluralityof inversely tapered partition walls 122 in parallel. Note that theidentical portions to those in FIGS. 5A to 5C are denoted by the samereference numerals.

The inversely tapered partition walls 122 are formed to be higher thanthe thickness of a layer including an organic compound and a conductivefilm. When a layer including an organic compound and a conductive filmare stacked over the first substrate having a structure shown in FIG. 6,they are separated into a plurality of regions which are electricallyisolated from each other, thereby layers (each including an organiccompound) 115R, 115G and 115B and second electrodes 116 are formed asshown in FIGS. 5A to 5C. The second electrodes 116 are stripedelectrodes which are provided in parallel and extend in a direction tointersect the first electrodes 113. Note that the layer including theorganic compound and the conductive film are also formed over theinversely tapered partition walls 122; however, they are separated fromthe layers (each including an organic compound) 115R, 115G and 115B andthe second electrodes 116.

This embodiment illustrates an example where the stacked layers 115R,115G and 115B each having a first composite layer including a metaloxide and an organic compound, a layer including an organic compound,and a second composite layer including a metal oxide and an organiccompound are selectively formed over the first electrode, so that alight-emitting device capable of performing full color display isprovided where three kinds of light emission (red, green and bluecolors) can be provided. The stacked layers 115R, 115G and 115B are eachformed in parallel with a stripe pattern. Although each stacked layerhas the same pattern, here, the first composite layer and the secondcomposite layer may be formed as a common layer to each light-emittingelement while only a layer including an organic compound to be alight-emitting layer may be selectively deposited using avapor-deposition mask.

An example of depositing a first composite layer including a metal oxideand an organic compound is shown. First, NPB and molybdenum oxide arestored in separate evaporation sources of resistance heating type, andthey are vapor-deposited onto a substrate having a first electrode whichis set inside an evacuated vapor-deposition system. At vapor deposition,NPB is vapor-deposited at a deposition rate of 0.4 nm/s while molybdenumoxide is vapor-deposited at an amount of 1/4 (weight ratio) relativelyto NPB. In this case, in terms of a molar ratio, NPB:molybdenum oxide is1:1. The first composite layer including a metal oxide and an organiccompound has a thickness of 50 nm.

Over the first composite layer, PPD(4,4′-bis(N-phenanthryl)-N-phenylamino)biphenyl) doped with CBP(4,4′-N,N′-dicarbazole-biphenyl) is deposited with a thickness of 30 nmas a blue light-emitting layer in a region for fowling a bluelight-emitting element.

In a region for forming a red light-emitting element, Alg_(a) doped withDCM is deposited with a thickness of 40 nm as a red light-emittinglayer.

In a region for forming a green light-emitting element, A1q₃ doped withDMQD is deposited with a thickness of 40 nm as a green light-emittinglayer.

Then, a second composite layer including a metal oxide and an organiccompound is formed over the blue light-emitting layer, the redlight-emitting layer and the green light-emitting layer. The secondcomposite layer is obtained by vapor-depositing NPB and molybdenum oxidesimilarly to the first composite layer. The second composite layer isalso fowled with a thickness of 50 nm. Note that the luminous efficiencymay be improved by appropriately changing the thickness of the firstcomposite layer and the second composite layer for each light-emissioncolor.

In addition, a light-emitting device capable of performing full colordisplay may be formed, where four kinds of light emission (red, green,blue and white) can be provided. Alternatively, a light-emitting devicecapable of performing full color display may be formed, where four kindsof light emission (red, green, blue and emerald green) can be provided.Further alternatively, a light-emitting device capable of performingfull color display may be faulted, where five kinds of light emission(red, green, blue, white and emerald green) can be provided. Inaddition, a light-emitting device capable of performing full colordisplay may be formed, where five kinds of light emission (red, green,blue, emerald green and orange) can be provided.

Alternatively, the layers may be stacked over the entire surface andmonochromatic light-emitting elements may be provided so that alight-emitting device capable of performing monochromatic display can beprovided, or a light-emitting device capable of performing area colordisplay can be provided. In addition, by combining a light-emittingdevice which provides white light emission with color filters, alight-emitting device capable of performing full color display may beformed.

The light-emitting element is sealed by attaching a second substrate tothe first substrate with a sealant. A protective film for covering thesecond electrode 116 may be formed as required. Note that the secondsubstrate is preferably a substrate having a high barrier propertyagainst moisture. In addition, a drying agent may be disposed in aregion surrounded by the sealant as required.

In the case where the first electrode 113 is formed using alight-reflective conductive material and the second electrode 116 isformed using a light-transmissive conductive material, a top-emissionlight-emitting device can be provided where light emitted fromlight-emitting elements is extracted through the second substrate. Thefirst electrode 113 is preferably formed using an aluminum alloy filmcontaining carbon and nickel in a single layer or using an aluminumalloy film containing carbon and nickel as a bottom layer of a stackwith a light-transmissive conductive film since the contact resistancevalue of the aluminum alloy film with ITO or ITSO does not fluctuatemuch even after current is applied thereto or heat treatment is applied.

In the case where the first electrode 113 is formed using alight-transmissive conductive material and the second electrode 116 isformed using a light-reflective conductive material, a bottom-emissionlight-emitting device can be provided where light emitted fromlight-emitting elements is extracted through the first substrate 110.

In the case where both the first electrode 113 and the second electrode116 are formed using a light-transmissive conductive material, adual-emission display device can be provided where light emitted fromlight-emitting elements is extracted through both the second substrateand the first substrate.

FIG. 7 is a top view of a light-emitting module on which an FPC and thelike are mounted after sealing.

A first substrate 301 and a second substrate 310 are attached with asealant 311 to face each other. The sealant 311 may be a photo-curingresin, and preferably a material having a low degasification propertyand a low hygroscopic property. A filler (spacer in a stick form orfiber form) or a spherical spacer may be added to the sealant 311 inorder to keep a constant gap between the substrates. Note that thesecond substrate 310 is preferably formed using a material which has theidentical thermal expansion coefficient to that of the first substrate301, and glass (including quartz glass) or plastic may be used.

In the pixel portion for displaying images, scan lines and data linesintersect each other as shown in FIG. 7.

The first electrode 113 in FIG. 5B corresponds to a data line 302 inFIG. 7, the second electrode 116 corresponds to a scan line 303, and theinversely tapered partition wall 122 corresponds to a partition wall304. A stack including an organic compound is interposed between thedata line 302 and the scan line 303, and an intersection denoted by 305corresponds to one pixel.

Note that the scan line 303 is electrically connected at its end to aconnecting wire 308, and the connecting wire 308 is connected to an FPC309 b through an input terminal 307. The data line 302 is connected toan FPC 309 a through an input terminal 306.

If necessary, a polarizing plate, a circularly polarizing plate(including an elliptically polarizing plate) or a retardation plate (aλ/4 plate or a λ/2 plate) and an optical film such as a color filter maybe appropriately provided on the light-emitting surface. Further, thepolarizing plate or the circulary polarizing plate may be provided withan anti-reflection film. For example, anti-glare treatment may becarried out by which reflected light can be diffused byprojections/depressions on the surface so as to reduce the glare. Inaddition, anti-reflection treatment by heat treatment may be applied tothe polarizing plate or the circulary polarizing plate. After that, hardcoat treatment is preferably applied in order to protect thelight-emitting module from external shocks. Note that the provision of apolarizing plate or a circulary polarizing plate will reduce the lightextraction efficiency. Further, the polarizing plate or the circularypolarizing plate itself is expensive and easily deteriorates.

The light-emitting module shown in FIG. 7 which is obtained in thismanner is driven with AC voltage. A light-emitting element of theinvention can emit light, even when driven with AC voltage, with both apositive signal and a negative signal being applied. Further, about anequal amount of light to the case of performing DC drive in which DCvoltage is applied can be obtained without increasing power consumption.

This embodiment can be freely implemented in combination with EmbodimentMode.

Embodiment 2

In this embodiment, description is made on an example of manufacture ofa light-emitting module on which an IC chip is mounted.

First, data lines (anodes) 402 each having a stacked-layer structure ofa reflective metal film as a bottom layer and a light-transmissiveconductive oxide film as a top layer are formed over a first substrate401 having an insulating surface. At the same time, connecting wires408, 409 a and 409 b and an input terminal are formed.

Subsequently, partition walls each having an opening corresponding toeach pixel 405 are formed. Then, a plurality of inversely taperedpartition walls 404 which are in parallel with each other and intersectthe data lines 402 are provided over the partition walls each having anopening.

FIG. 8A shows a top view obtained through the aforementioned steps.

Then, a first composite layer including a metal oxide and an organiccompound, a layer including an organic compound, a second compositelayer including a metal oxide and an organic compound, and alight-transmissive conductive film are sequentially stacked, so that thelayers are separated into a plurality of regions which are electricallyinsulated from each other as shown in FIG. 8B, thereby a layer includingan organic compound and scan lines 403 formed of a light-transmissiveconductive film are formed. The scan lines 403 formed of thelight-transmissive film are striped electrodes which are in parallelwith each other and extend in a direction to intersect the data lines402.

Then, a light-transmissive second substrate 414 is attached to the firstsubstrate 401 with a sealant 413. Then, a data line side IC 406 and ascan line side IC 407 in each of which a driver circuit for transmittingeach signal to the pixel portion is formed are mounted onto a regionaround (outside) the pixel portion by COG bonding. As an alternativemounting technique to the COG bonding, TCP or wire bonding may be used.TCP is a TAB tape on which an IC is mounted, and the IC is mounted byconnecting the TAB tape to wires on the element forming substrate. Eachof the data line side IC 406 and the scan line side IC 407 may be formedusing a silicon substrate. Alternatively, it may be a driver circuitformed using TFTs over a glass substrate, a quartz substrate or aplastic substrate. Although shown here is an example in which a singleIC is provided on one side, a plurality of ICs may be provided on oneside.

Note that the scan lines 403 are electrically connected at their ends tothe connecting wire 408, and the connecting wire 408 is connected to thescan line side IC 407. This is because it is difficult to provide thescan line side IC 407 over the inversely tapered partition walls 404.

The data line side IC 406 provided with the aforementioned structure isconnected to an FPC 411 through the connecting wire 409 a and an inputterminal 410. The scan line side IC 407 is connected to an FPC throughthe connecting wire 409 b and an input terminal.

Further, an IC chip 412 (e.g., a memory chip, a CPU chip or a powersource circuit chip) is mounted to achieve higher integration.

FIG. 9 shows an example of a cross-sectional structure along a dashedline C-D in FIG. 8B.

A base insulating film 511 is provided over a substrate 510, over whichdata lines each having a stacked-layer structure are formed. A bottomlayer 512 is a reflective metal film while a top layer 513 is alight-transmissive conductive oxide film. The top layer 513 ispreferably formed using a conductive film having a high work function,for example a light-transmissive conductive material such as indium tinoxide (ITO), indium tin oxide containing Si elements (ITSO) or IZO(Indium Zinc Oxide) obtained by mixing indium oxide with 2 to 20wt % ofzinc oxide (ZnO), or a film containing a compound of such conductivematerials. Above all, ITSO remains to be, even when baked, in anamorphous state without being crystallized unlike ITO. Accordingly, ITSOhas higher planarity than ITO, and does not easily short-circuit to acathode even when a stack including an organic compound is thin. Thus,ITSO is suitable for an anode of a light-emitting element.

The bottom layer 512 is formed using Ag, Al or an Al(C, Ni) alloy film.Above all, the Al(C, Ni) film (an aluminum alloy film containing carbonand nickel (by 1 to 20 wt %)) is a material which has few fluctuationsin the contact resistance value with ITO or ITSO even after current isapplied thereto or heat treatment is applied.

A partition wall 514 is a resin for insulating adjacent data lines, andoverlaps the boundary or gap between different colored layers (which areprovided on the sealing substrate side). A region surrounded by thepartition wall has the same area as the light-emitting region.

A layer including an organic compound 515 has a stack of a firstcomposite layer, an EML (light-emitting layer) and a second compositelayer in this order from the date line (anode) side.

Each of the first composite layer and the second composite layer is acomposite layer including a metal oxide and an organic compound. In thisembodiment, a composite layer of tungsten oxide and TPD is used. The EML(light-emitting layer) is formed using a light-emitting substance. Atthis time, the light-emitting layer may be formed in such a manner thata light-emitting substance is dispersed in a layer containing asubstance having a larger energy gap than the energy gap of thelight-emitting substance. By dispersing the light-emitting substance,loss of light due to the concentration can be prevented. Thelight-emitting substance is not specifically limited to a certain type.In the case of obtaining red light emission, a substance which exhibitslight emission having a light-emission spectrum with a peak of 600 to680 nm may be used as the light-emitting substance. For example, thereare4-(dicyano-methylene)-2-isopropyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran(abbreviated as DCJTI);4-(dicyano-methylene)-2-methyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran(abbreviated as DCJT);4-(dicyano-methylene)-2-tert-butyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran(abbreviated as DCJTB); periflanthene;2,5-dicyano-1,4-bis[2-(10-methoxy-1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]benzene;and the like. In the case of obtaining green light emission, alight-emitting substance which exhibits light emission having alight-emission spectrum with a peak of 500 to 550 nm may be used as thelight-emitting substance. For example, there are N,N′-dimethylquinacridone (abbreviated as DMQd); Coumarin 6; Coumarin 545T;tris(8-quinolinolato) aluminum (abbreviated as Alq₃); and the like. Inthe case of obtaining blue light emission, a light-emitting substancewhich exhibits light emission having a light-emission spectrum with apeak of 420 to 500 nm may be used as the light-emitting substance. Forexample, there are 9,10-bis(2-naphthyl)-2-tert-butylanthracene(abbreviated as t-BuDNA); 9,9′ -biantolyl,9,10-diphenylanthracene(abbreviated as DPA); 9,10-di(2-naphthyl)anthracene (abbreviated asDNA); bis(2-methyl-8-quinolinolate)-4-phenylphenolate-gallium(abbreviated as BGaq);bis(2-methyl-8-quinolinolate)-4-phenylphenolate-aluminum (abbreviated asBAlq); and the like. In addition, the substance used in combination withthe dispersed light-emitting substances is not limited to a certain typeeither. For example, there are anthracene derivatives such as9,10-bis(2-naphthyl)-2-tert-butylanthracene (abbreviated as t-BuDNA);carbazole derivatives such as 4,4′-bis(N,N′-carbazole)biphenyl(abbreviated as CBP); a metal complex such asbis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviated as Znpp₂) orbis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviated as ZnBOX); andthe like.

Note that the EML may have a stacked-layer structure or a mixedstructure as well as a single-layer structure.

A scan line 516 (cathode) is formed to intersect the data line (anode).The scan line 516 (cathode) is formed of a light-transmissive conductivefilm such as ITO, indium tin oxide containing Si elements (ITSO), andIZO obtained by mixing indium oxide with 2 to 20 wt % of zinc oxide(ZnO). This embodiment illustrates an example of a top-emissionlight-emitting device where light is emitted through a sealing substrate520. Therefore, the scan line 516 is required to transmit light.

In order to protect light-emitting elements from damage due to moistureor degasification, a light-transmissive protective film may be providedfor covering the scan line 516. The light-transmissive protective filmis preferably a dense inorganic insulating film (e.g., a SiN film or aSiNO film) formed by PCVD, a dense inorganic insulating film (e.g., aSiN film or a SiNO film) fowled by sputtering, a thin film containingcarbon as a main component (e.g., a DLC film, a CN film or an amorphouscarbon film), a metal oxide film (e.g., WO₂ or Al₂O₃), CaF₂ or the like.

A pixel portion including light-emitting elements is sealed withsealants 519 and the sealing substrate 520, and the space surroundedtherebetween is sealed hermetically.

The sealants 519 may be an ultraviolet-curing resin, a heat-curing rein,a silicone resin, an epoxy resin, an acrylic rein, a polyimide resin, aphenol resin, a PVC (polyvinyl chloride), PVB (polyvinyl butyral) or EVA(ethylene vinyl acetate). In addition, the sealants 519 may be providedwith a filler (spacer in a stick form or fiber form) or a sphericalspacer.

The sealing substrate 520 is a glass substrate or a plastic substrate.The plastic substrate may be polyimide, polyamide, an acrylic resin, anepoxy resin, PES (polyether sulfone), PC (polycarbonate), PET(polyethylene terephthalate) or PEN (polyethylene naphthalate) in theform of a plate or a film.

Note that a sealed space 518 is filled with a dried inert gas. A slightamount of moisture in the sealed space 518 surrounded by the sealants519 is removed by a drying agent 517, and thus is sufficiently dried.The drying agent 517 may be a substance which absorbs moisture bychemical adsorption such as an oxide of an alkaline earth metal astypified by calcium oxide or barium oxide. Note that a substance whichadsorbs moisture by physical adsorption such as zeolite or silica gelmay be used as well.

At the edge of the substrate 510, a terminal electrode is formed, and anFPC (flexible printed wiring board) 532 for connection to an externalcircuit is attached to this portion. Although the terminal electrode isa stack of a reflective metal film 530, a light-transmissive conductiveoxide film 529, and a conductive oxide film extending from the secondelectrode, or a stack of a reflective metal film 527 and alight-transmissive conductive oxide film 526, the invention is notlimited to this.

As a method for mounting the FPC 532, a connecting method using ananisotropic conductive material or a metal bump or a wire bonding methodcan be used. In FIG. 9, connection is carried out by using ananisotropic conductive adhesive material 531.

On the periphery of the pixel portion, an IC chip 523 in which a drivercircuit for transmitting each signal to the pixel portion is formed iselectrically connected with anisotropic conductive materials 524 and525. In order to form a pixel portion corresponding to color display,3072 data lines and 768 scan lines are required for the XGA displayclass. Such number of the data lines and scan lines are segmented perseveral blocks at an edge of the pixel portion, and then gathered inaccordance with the pitch of output terminals of ICs.

This embodiment can be freely implemented in combination with EmbodimentMode or Embodiment 1.

Embodiment 3

In this embodiment, description is made with reference to FIG. 10A on anexample of providing an optical film.

Over a second substrate 620 provided to face a first substrate 610, anoptical film 621 is provided. This embodiment illustrates an examplewhere light is emitted in the direction shown by the arrows in FIG. 10A,specifically an example where light emitted from light-emitting elementspasses through the second substrate 620 first and then through theoptical film 621. However, the invention is not limited to this and theoptical film may be provided on the first substrate side so that thelight emitted from light-emitting elements passes through the opticalfilm first and then through the first substrate 610.

The optical film 621 means a polarizing plate, a circularly polarizingplate (including an elliptically polarizing plate), a retardation plate(a λ/4 plate or a λ/2 plate) or an optical film such as a color filter.

A light-emitting element in a pixel of a passive matrix light-emittingdevice includes, similarly to Embodiment 1, a data line (anode) having astacked-layer structure of a bottom layer 612 formed of a reflectivemetal film and a top layer 613 formed of a light-transmissive conductiveoxide film, a first material layer 615 a, a layer including an organiccompound 615 b, a second material layer 615 c and a scan line (cathode)616 formed of a light-transmissive conductive film. A partition wall 614is formed of a resin material.

Note that each of the first material layer 615 a and the second materiallayer 615 c is a composite layer of a metal oxide (e.g., molybdenumoxide, tungsten oxide or rhenium oxide) and an organic compound(material having a hole transporting property). By adopting such astacked-layer structure of a light-emitting element, a light-emittingelement suitable for AC drive is obtained.

If a circulary polarizing plate is used as the optical film 621, it canbe prevented that the visibility of images is decreased due to theexternal light reflected on the lower layer 612. Note that thecircularly polarizing plate means a circularly polarizing plate(including an elliptically polarizing plate) which has a combination ofa retardation plate or a retardation film having a phase-shiftingproperty of, specifically, λ/4 or λ/4+λ/2, with a polarizing plate, apolarizing film or a linearly polarizing film. The λ/4 plate herein hasa broad band and shifts the phase of visible light by 90 degrees.Specifically, the circularly polarizing plate defined herein isconstructed in such a manner that the transmission axis of a polarizingplate and the phase-shifting axis of a retardation film make an angle of45 degrees. Note that in this specification, the circulary polarizingplate includes a circularly polarizing film.

Additionally, full color display can be performed by using whitelight-emitting elements in combination with a color filter as theoptical film 621.

Alternatively, several kinds of optical films may be appropriatelycombined.

This embodiment can be freely implemented in combination with EmbodimentMode, Embodiment 1 or Embodiment 2.

Embodiment 4

In this embodiment, description is made with reference to FIG. 10B on anexample of a bottom-emission light-emitting device.

A light-emitting element in this embodiment includes a data line (anode)713 formed of a light-transmissive conductive oxide film, a firstmaterial layer 715 a, a layer including an organic compound 715 b, asecond material layer 715 c, and a scan line (cathode) 716 formed of areflective conductive film. A partition wall 714 is formed of a resinmaterial similarly to Embodiment 3.

Note that each of the first material layer 715 a and the second materiallayer 715 c is a composite layer of a metal oxide (e.g., molybdenumoxide, tungsten oxide or rhenium oxide) and an organic compound(material having a hole transporting property). By adopting such astacked-layer structure of a light-emitting element, a light-emittingelement suitable for AC drive is obtained.

Light emitted from light-emitting elements is extracted in the directionof the arrows shown in FIG. 10B, specifically through a first substrate710. Accordingly, a second substrate 721 is not specifically required totransmit light, and it may be a metal plate. A thick protective film 717may be preferably provided in order to improve the reliability of thelight-emitting element, since the light extraction efficiency is notdecreased thereby.

This embodiment can be freely implemented in combination with any ofEmbodiment Mode, Embodiment 1, Embodiment 2 and Embodiment 3. Forexample, this embodiment may be combined with Embodiment 3, and in thecase of providing an optical film, the optical film may be provided overthe first substrate 710.

Embodiment 5

In this embodiment, description is made with reference to FIG. 10C on anexample of a light-emitting device which is different from those inEmbodiments 1 to 4.

A light-emitting element in this embodiment includes a data line (anode)813 formed of a light-transmissive conductive oxide film, a firstmaterial layer 815 a, a layer including an organic compound 815 b, asecond material layer 815 c and a scan line (cathode) 816 formed of alight-transmissive conductive oxide film. A partition wall 814 is formedof a resin material similarly to Embodiment 3.

Note that each of the first material layer 815 a and the second materiallayer 815 c is a composite layer of a metal oxide (e.g., molybdenumoxide, tungsten oxide or rhenium oxide) and an organic compound(material having a hole transporting property). By adopting such astacked-layer structure of a light-emitting element, a light-emittingelement suitable for AC drive is obtained.

Light emitted from light-emitting elements is extracted in the directionof the arrows shown in FIG. 10C, specifically through both a firstsubstrate 810 and a second substrate 820. Accordingly, each of the firstsubstrate 810 and the second substrate 820 is formed of alight-transmissive substrate.

This embodiment can be freely implemented in combination with any ofEmbodiment Mode, Embodiment 1, Embodiment 2 and Embodiment 3. Forexample, this embodiment may be combined with Embodiment 3, and in thecase of providing an optical film, the optical film may be provided overeach of the first substrate 810 and the second substrate 820.

Embodiment 6

The light-emitting device and electronic appliance of the inventionincludes a camera (e.g., a video camera or a digital camera), anavigation system, an audio reproducing system (e.g., car audio set oran audio component stereo), a personal computer, a game machine, aportable information terminal (e.g., a mobile computer, a portablephone, a portable game machine or an electronic book), an imagereproducing device provided with a recording medium (specifically, adevice for reproducing a recording medium such as a digital versatiledisc (DVD) and having a display for displaying the reproduced image) andthe like. FIGS. 11 and 12 show specific examples of such electronicappliances.

A portable phone shown in FIG. 11 includes a main body (A) 901 providedwith an operating switch 904, a microphone 905 and the like, and a mainbody (B) 902 provided with a display panel (A) 908, a display panel (B)909, a speaker 906 and the like, which are connected with a hinge 910 sothat the portable phone can be opened or folded. The display panel (A)908 and the display panel (B) 909 are incorporated into housings 903 ofthe main body (B) 902 ZS together with a circuit board 907. Pixelportions of the display panel (A) 908 and the display panel (B) 909 aredisposed so that they can be seen from open windows formed in thehousings 903.

The specifications of the display panel (A) 908 and the display panel(B) 909 such as the number of pixels can be appropriately set inaccordance with the function of the portable phone 900. For example, thedisplay panel (A) 908 and the display panel (B) 909 can be used incombination so as to be used as a main display screen and a sub-displayscreen respectively.

The display panel (A) 908 has a structure shown in any one ofEmbodiments 1 to 5 so that AC drive can be performed. According to theinvention, the total power consumption of the portable phone can besuppressed without causing an increase in the driving voltage even whenthe display panel (A) 908 is driven with AC voltage. Similarly, thedisplay panel (B) 909 may also be driven with AC voltage, thereby thetotal power consumption of the portable phone can be suppressed withoutcausing an increase in the driving voltage.

The portable phone of this embodiment can be changed into various modesin accordance with the function or applications. For example, byincorporating an image pick-up device into the hinge 910, a portablephone equipped with a camera can be provided. In addition, if theoperating switch 904, the display panel (A) 908 and the display panel(B) 909 are incorporated into one housing, the aforementioned effect canbe obtained. Further, if the structure of this embodiment is applied toan information display terminal having a plurality of display portions,a similar effect can be obtained.

FIG. 12A is a television set including a housing 2001, a supporting base2002, a display portion 2003, a speaker portion 2004, a video inputterminal 2005 and the like. According to the invention, the displayportion 2003 incorporated in the television set is driven with ACvoltage, thereby a television with low power consumption can beprovided. Note that the television set includes television sets forvarious information displays such as personal computers, TV broadcastreception and advertisement display.

FIG. 12B is a digital camera which includes a main body 2101, a displayportion 2102, an image receiving portion 2103, operating keys 2104, anexternal connection port 2105, a shutter 2106 and the like. According tothe invention, the display portion 2102 incorporated in the digitalcamera is driven with AC voltage, thereby a digital camera with lowpower consumption can be provided.

FIG. 12C is a personal computer which includes a main body 2201, ahousing 2202, a display portion 2203, a keyboard 2204, an externalconnection port 2205, a pointing mouse 2206 and the like. According tothe invention, the display portion 2203 incorporated in the personalcomputer is driven with AC voltage, thereby a personal computer with lowpower consumption can be provided.

FIG. 12D is an electronic book which includes a main body 2301, adisplay portion 2302, a switch 2303, operating keys 2304, an IR port2305 and the like. According to the invention, the display portion 2302incorporated in the electronic book is driven with AC voltage, therebyan electronic book with low power consumption can be provided.

FIG. 12E is a portable image reproducing device provided with arecording medium (specifically, a DVD reproducing device), whichincludes a main body 2401, a housing 2402, a display portion 2403, adisplay portion 2404, a recording medium (e.g., DVD) reading portion2405, an operating key 2406, a speaker portion 2407 and the like. Thedisplay portion 2403 mainly displays image data while the displayportion 2404 mainly displays text data. According to the invention, thedisplay portions 2403 and 2404 incorporated in the image reproducingdevice are driven with AC voltage, thereby an image reproducing devicewith low power consumption can be provided.

FIG. 12F is a portable game machine which includes a main body 2501, adisplay portion 2505, an operating switch 2504 and the like. Accordingto the invention, the display portion 2505 incorporated in the gamemachine is driven with AC voltage, thereby a portable game machine withlow power consumption can be provided.

FIG. 12G is a video camera which includes a main body 2601, a displayportion 2602, a housing 2603, an external connection port 2604, a remotecontroller receiving portion 2605, an image receiving portion 2606, abattery 2607, an audio input portion 2608, an eyepiece portion 2609,operating keys 2610 and the like. According to the invention, thedisplay portion 2602 incorporated in the video camera is driven with ACvoltage, thereby a video camera with low power consumption can beprovided.

This embodiment can be freely implemented in combination with EmbodimentMode, Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4 orEmbodiment 5.

According to the invention, the structure of an EL element using ACdrive as well as a manufacturing process thereof can be simplified.Further, according to the invention, a pair of electrodes of an ELelement can be controlled to be thick without causing an increase in thedriving voltage; therefore, a short circuit of elements which derivesfrom dust or the like in the formation process of the EL element can besuppressed, thereby the yield can be improved.

The present application is based on Japanese Priority application No.2004-353427 filed on Dec. 6, 2004 with the Japanese Patent Office, theentire contents of which are hereby incorporated by reference.

1-10. (canceled)
 11. A light-emitting device comprising: a firstelectrode; a first composite layer formed over the first electrode, thefirst composite layer including a first metal oxide and a first organiccompound; a light emitting layer comprising an organic material formedover the first composite layer; a second composite layer formed over thelight emitting layer, the second composite layer including a secondmetal oxide and a second organic compound; and a second electrode formedover the second composite layer.
 12. The light-emitting device accordingto claim 11, wherein the first composite layer has symmetriccurrent-voltage characteristics with respect to the zero point in agraph having the abscissa axis showing current values and the ordinateaxis showing voltage values; and wherein the second composite layer hasthe same current-voltage characteristic as the first composite layer.13. The light-emitting device according to claim 11, wherein the firstmetal oxide and the second metal oxide are the same material, and thefirst organic compound and the second organic compound are the samematerial.
 14. The light-emitting device according to claim 11, whereinthe light-emitting device is of a passive matrix type.
 15. Thelight-emitting device according to claim 11, wherein the first metaloxide and the second metal oxide are one or more of molybdenum oxide,tungsten oxide and rhenium oxide.
 16. The light-emitting deviceaccording to claim 11, wherein the first composite layer and the secondcomposite layer have both a hole injection property and an electroninjection property.
 17. The light-emitting device according to claim 11,wherein the first composite layer and the second composite layer haveboth a hole transport property and an electron transport property. 18.The light-emitting device according to claim 11, wherein thelight-emitting device is a lighting device.
 19. The light-emittingdevice according to claim 11, further comprising a sealing substrateprovided with a drying agent.
 20. A light-emitting device comprising: afirst electrode; a first composite layer formed over the firstelectrode, the first composite layer including a first metal oxide and afirst organic compound; a light emitting layer comprising an organicmaterial formed over the first composite layer; a second composite layerformed over the light emitting layer, the second composite layerincluding a second metal oxide and a second organic compound; and asecond electrode formed over the second composite layer, wherein thelight emitting layer has a HOMO level and a LUMO level within a bandgapof the first and second metal oxides.
 21. The light-emitting deviceaccording to claim 20, wherein the first composite layer has symmetriccurrent-voltage characteristics with respect to the zero point in agraph having the abscissa axis showing current values and the ordinateaxis showing voltage values; and wherein the second composite layer hasthe same current-voltage characteristic as the first composite layer.22. The light-emitting device according to claim 20, wherein the firstmetal oxide and the second metal oxide are the same material, and thefirst organic compound and the second organic compound are the samematerial.
 23. The light-emitting device according to claim 20, whereinthe light-emitting device is of a passive matrix type.
 24. Thelight-emitting device according to claim 20, wherein the first metaloxide and the second metal oxide are one or more of molybdenum oxide,tungsten oxide and rhenium oxide.
 25. The light-emitting deviceaccording to claim 20, wherein the first composite layer and the secondcomposite layer have both a hole injection property and an electroninjection property.
 26. The light-emitting device according to claim 20,wherein the first composite layer and the second composite layer haveboth a hole transport property and an electron transport property. 27.The light-emitting device according to claim 20, wherein thelight-emitting device is a lighting device.
 28. The light-emittingdevice according to claim 20, further comprising a sealing substrateprovided with a drying agent.
 29. A light-emitting device comprising: afirst electrode disposed in a stripe form; a first composite layerformed over the first electrode, the first composite layer including afirst metal oxide and a first organic compound; a light emitting layercomprising an organic material formed over the first composite layer; asecond composite layer formed over the light emitting layer, the secondcomposite layer including a second metal oxide and a second organiccompound; and a second electrode formed over the second composite layer,the second electrode being disposed in a stripe form perpendicular tothe first electrode, wherein the first electrode is formed using alight-reflective conductive material; and wherein the second electrodeis formed using a light-transmissive conductive material.
 30. Thelight-emitting device according to claim 29, wherein the first compositelayer has symmetric current-voltage characteristics with respect to thezero point in a graph having the abscissa axis showing current valuesand the ordinate axis showing voltage values; and wherein the secondcomposite layer has the same current-voltage characteristic as the firstcomposite layer.
 31. The light-emitting device according to claim 29,wherein the first metal oxide and the second metal oxide are the samematerial, and the first organic compound and the second organic compoundare the same material.
 32. The light-emitting device according to claim29, wherein the first metal oxide and the second metal oxide are one ormore of molybdenum oxide, tungsten oxide and rhenium oxide.
 33. Thelight-emitting device according to claim 29, wherein the first compositelayer and the second composite layer have both a hole injection propertyand an electron injection property.
 34. The light-emitting deviceaccording to claim 29, wherein the first composite layer and the secondcomposite layer have both a hole transport property and an electrontransport property.
 35. The light-emitting device according to claim 29,wherein the light-emitting device is a lighting device.
 36. Thelight-emitting device according to claim 29, further comprising asealing substrate provided with a drying agent.